Human vocal cords and other soft tissues of the larynx occasionally require medication or augmentation. Medication often takes the form of anesthesia. Augmentation can, for example, be required to replace diseased tissue that has been removed surgically, or it can be required to correct a naturally occurring inadequate seal between the vocal cords. Preferably, the augmentation is carried out nonsurgically by injecting a suitable paste or fluid substance into the tissue requiring augmentation. A paste of poly(tetrafluoroethylene) (Teflon.RTM.) has been used for the purpose in the past (see, for example, Ward, "Uses of Injectable Teflon in Otolaryngology", Arch Otolaryng, vol. 87, June 1968, pp. 91-97).
Recently, Collagen Corporation has suggested that essentially nonantigenic exogenous collagen could be used for treating this indication. An essentially nonantigenic bovine collagen for augmenting soft tissue defects has ben marketed by Collagen Corporation under the trademark ZYDERM.RTM.. An injectable glutaraldehyde cross-linked form of this collagen has been developed for the same use and is described in published European Patent Application No. 83301135.6 (published on Sept. 21, 1983).
In such an application, collagen offers a number of advantages. For one, it is very persistent--that is, it is not prone to migration or dispersal after injection. It is very biocompatible and has the potential for administration with greater accuracy and precision because it is relatively low in viscosity as compared with the Teflon pastes. Proteoglycan and other low viscosity natural or synthetic biopolymers can be used as well.
In order to realize these advantages, however, special injection devices are required to enable the collagen suspension to be properly and precisely delivered to the relatively inaccessible tissues of the larynx. It is an object of this invention to provide such an injection device.